使用NaturalDuration获取音频的时长

#region customizeTime
                if (mediaElement.NaturalDuration.TimeSpan.Seconds < )
                    sec = "" + mediaElement.Position.Seconds.ToString();
                else
                    sec = mediaElement.NaturalDuration.TimeSpan.Seconds.ToString();

                if (mediaElement.NaturalDuration.TimeSpan.Minutes < )
                    min = "" + mediaElement.NaturalDuration.TimeSpan.Minutes.ToString();
                else
                    min = mediaElement.NaturalDuration.TimeSpan.Minutes.ToString();

                if (mediaElement.NaturalDuration.TimeSpan.Hours < )
                    hours = "" + mediaElement.NaturalDuration.TimeSpan.Hours.ToString();
                else
                    hours = mediaElement.NaturalDuration.TimeSpan.Hours.ToString();

                if (mediaElement.NaturalDuration.TimeSpan.Hours == )
                {

                    endTimeTextBlock.Text = min + ":" + sec;
                }
                else
                {
                    endTimeTextBlock.Text = hours + ":" + min + ":" + sec;
                }

                #endregion customizeTime